JPH1017711A - Anti-vibration rubber composition - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a rubber composition which is excellent in soundproof / vibration-proof characteristics at room temperature and low-temperature characteristics. SOLUTION: The rubber composition contains (a) 50 to 95% by weight of an isoprene-based rubber and (b) 5 to 50% by weight of a nitrile group-containing unsaturated copolymer rubber as rubber components.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-vibration rubber composition and, more particularly, to an anti-vibration rubber composition which is excellent in soundproof / vibration-proof characteristics at room temperature and low-temperature characteristics, and is particularly practical for low-temperature use.

[0002]

2. Description of the Related Art In general, isoprene rubbers such as polyisoprene rubber and natural rubber have good soundproofing and vibrationproofing properties. When these rubbers are used as vibration damping rubbers, it is known that, for example, a styrene-butadiene rubber having a styrene content of about 35% by weight is blended with an isoprene-based rubber in order to increase the damping property. However, since the styrene-butadiene rubber having a high styrene content has a glass transition point of -30 to 35 ° C., it becomes hard at low temperatures, and is difficult to use as a vibration-proof rubber material for an automobile running in an extremely cold region, for example. There were drawbacks.

On the other hand, a nitrile group-containing highly saturated copolymer rubber obtained by hydrogenating the unsaturated bond portion of an unsaturated nitrile-conjugated diene copolymer rubber also has good vibration damping properties at room temperature. It is known to use a saturated copolymer rubber alone or as a blend with another rubber as an anti-vibration rubber material (Japanese Patent Application Laid-Open No. 62-96543).
No. JP-A-4-246439). However, the performance requirements for rubber materials are expanding year by year, and although rubber materials that have good low-temperature characteristics in addition to good vibration damping performance are also one of the rubber materials that are highly demanded, nitrile group-containing highly saturated Copolymer rubber is inferior in cold resistance properties and cannot meet this demand.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide an anti-vibration rubber material which is excellent in sound and vibration proof characteristics at room temperature and low-temperature characteristics. As a result of repeated studies to achieve the above object, the present inventors have found that a natural rubber blended with an unsaturated nitrile-conjugated diene copolymer rubber has good and balanced cold resistance and vibration isolation at room temperature. They have found that they have both characteristics and have completed the present invention.

Thus, according to the present invention, the rubber component comprises (a) 50 to 95% by weight of an isoprene-based rubber and (b) 5 to 50% by weight of a nitrile group-containing unsaturated copolymer rubber. Is provided.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The isoprene-based rubber which is one of the main components of the vibration-proof rubber composition of the present invention refers to a rubber comprising isoprene units and a rubber containing at least 30% by weight of isoprene units. Examples include natural rubber and polyisoprene rubber. The isoprene-based rubber used in the present invention preferably has a Mooney viscosity ML4 of _{40 to} 200, particularly preferably 50 to 100.

[0007] The nitrile group-containing unsaturated copolymer rubber, which is another main component of the vibration damping rubber composition of the present invention, comprises an ethylenically unsaturated nitrile unit, a conjugated diene unit and / or an ethylenically unsaturated monomer. A copolymer rubber composed of units, usually having a Mooney viscosity of 150 or less, preferably 8
0 or less, and the iodine value is greater than 120, preferably 2
00 to 400. When the iodine value is 120 or less, the damping property is good, but the cold resistance is poor. It is also possible to use a liquid nitrile group-containing unsaturated copolymer rubber.

The nitrile group-containing unsaturated copolymer rubber used in the present invention includes an unsaturated nitrile-conjugated diene copolymer rubber, an unsaturated nitrile-conjugated diene-ethylenically unsaturated monomer terpolymer. Rubbers and unsaturated nitrile-ethylenically unsaturated monomer copolymer rubbers. These nitrile group-containing unsaturated copolymer rubbers can be obtained by using ordinary polymerization techniques, but it goes without saying that the production method itself is not particularly limited.

The following are the monomers used for producing the nitrile group-containing unsaturated copolymer rubber. As unsaturated nitriles, acrylonitrile, methacrylonitrile,
α-chloroacrylonitrile and the like can be mentioned, and among them, acrylonitrile is preferable. Examples of the conjugated diene include 1,3-butadiene, 2,3-dimethylbutadiene, isoprene, and 1,3-pentadiene, and among these, 1,3-butadiene and isoprene are preferred. Examples of the ethylenically unsaturated monomer include acrylic acid, methacrylic acid, itaconic acid, unsaturated carboxylic acids such as maleic acid and salts thereof; methyl acrylate,
Esters of the carboxylic acids such as 2-ethylhexyl acrylate; alkoxyalkyl esters of the unsaturated carboxylic acids such as methoxymethyl acrylate and ethoxyethyl acrylate; acrylamide, methacrylamide; N-methylol (meth) acrylamide;
N, N'-dimethylol (meth) acrylamide, N-
N-substituted (meth) acrylamides such as ethoxymethyl (meth) acrylamide and the like are included.

In the unsaturated nitrile-ethylenically unsaturated monomer copolymer rubber, a part of the unsaturated monomer may be substituted with a non-conjugated diene such as vinyl norbornene or dicyclopentadiene for copolymerization.

Specific examples of the nitrile group-containing unsaturated copolymer rubber used in the present invention include butadiene-acrylonitrile copolymer rubber, isoprene-butadiene-acrylonitrile copolymer rubber, isoprene-acrylonitrile copolymer rubber and the like. Unsaturated nitrile-conjugated diene copolymer rubber; butadiene-methyl acrylate-acrylonitrile copolymer rubber, butadiene-acrylic acid-acrylonitrile copolymer rubber, and other unsaturated nitrile-conjugated diene-ethylenically unsaturated monomer copolymer rubber; Polymer rubber; butadiene-ethylene-acrylonitrile copolymer rubber, butyl acrylate-ethoxy acrylate-vinyl chloroacetate-acrylonitrile copolymer rubber, butyl acrylate-ethoxyethyl acrylate-vinyl norbornene-ac Unsaturated nitriles such as Ronitoriru copolymer rubber - include the ethylenically unsaturated monomer copolymer rubbers.

The content of bound unsaturated nitrile in the nitrile group-containing unsaturated copolymer rubber is preferably from 10 to 40% by weight, more preferably from 15 to 30% by weight.
The proportions of the isoprene-based rubber and the nitrile group-containing unsaturated copolymer rubber are 50 to 95% by weight of the isoprene-based rubber and 5 to 50% by weight of the nitrile group-containing unsaturated copolymer rubber based on 100 parts by weight of both rubbers. It is. If the amount of the isoprene-based rubber is too large, the damping characteristics are lowered, and if the amount of the nitrile group-containing unsaturated copolymer rubber is too large, the low-temperature characteristics are inferior.

In the present invention, other rubbers can be mixed in addition to the above-mentioned isoprene-based rubber and the nitrile group-containing unsaturated copolymer rubber. Other rubbers to be mixed include styrene-butadiene rubber, polybutadiene rubber and ethylene-α-olefin-non-conjugated diene copolymer rubber (EP
DM) and the like. The amount of these rubbers is 50 parts by weight or less based on 100 parts by weight of the total of the isoprene-based rubber and the nitrile group-containing unsaturated copolymer rubber. The rubber composition of the present invention is obtained by mixing various compounding agents commonly used in the rubber industry in addition to the above-mentioned rubber using an ordinary mixer to obtain a compounded rubber composition. The type and amount of the compounding agent are determined according to the purpose of use of the rubber composition, and are not particularly limited in the present invention.

The compounding agents include sulfur or sulfur-donating compounds such as tetramethylthiuram disulfide, vulcanization aids such as zinc white and stearic acid, and guanidine, thiazole, thiuram and dithioate salts. Sulfur vulcanization system composed of vulcanization accelerators; various grades of carbon black such as HAF and FEF; reinforcing agents such as silica and talc; fillers such as calcium carbonate and clay; aroma-based, naphthenic and paraffin-based processes Plasticizers such as oil and dioctyl phthalate; processing aids, antioxidants and the like are usually used.

The amounts of the various compounding agents may be those commonly used in various rubber compositions. Generally, 10 to 100 parts by weight of a reinforcing agent and 10 to 10 parts by weight of a filler are added to 100 parts by weight of a rubber component.
0 parts by weight, plasticizer 5 to 50 parts by weight, antioxidant 0.01
-5 parts by weight, sulfur-based vulcanizing agent 0.1-10 parts by weight, sulfur-based vulcanization accelerator 0.1-10 parts by weight, vulcanization aid 0.1-20
Parts by weight are used.

[0016]

The present invention will be specifically described below with reference to examples and comparative examples. The anti-vibration characteristics in Examples and Comparative Examples were evaluated by loss tangent (tan δ) measured at 23 ° C. and 15 Hz using dynamic servo. ta
The larger the nδ value, the higher the damping property and the better the vibration damping property. The low-temperature characteristics were measured using a Gehman torsion tester at temperatures T10 and T100 when the specific modulus was 10 times and 100 times that at low temperature (23 ° C.), respectively. The lower the temperature, the better the cold resistance. Further, physical properties in normal state, that is, tensile strength (TB, MPa), elongation (TB,%), 1
00% tensile stress (M100, MPa) is JIS-K63
According to a tensile test performed in accordance with No. 01. The hardness (HS) was measured using a JIS spring type A hardness tester.

The rubber components used in Examples 1 to 3 and Comparative Examples 1 to 3 are as follows. (A) Natural rubber (MSR # 3) (B) Acrylonitrile-butadiene copolymer rubber (N
BR, bound acrylonitrile amount 18 wt%, Mooney viscosity ML _4: 80, iodine value: 330) (c) a styrene - butadiene copolymer rubber (SBR-
1. Bound styrene content: 25% by weight, Mooney viscosity M
L _4: 55)

(D) Styrene-butadiene copolymer rubber (SBR-2, bound styrene content: 40% by weight, Mooney viscosity ML ₄ : 45) (e) Hydrogenated acrylonitrile-butadiene copolymer rubber (HNBR, bound acrylonitrile) Amount: 36% by weight,
Mooney viscosity ML ₄ : 80) The rubber component and various compounding agents were compounded in a small Banbury mixer (1.8 liter volume) in a volume ratio of 75% in accordance with the formulations shown in Tables 1 and 2.

The temperature is raised to 50 ° C. with warm water, and first the rubber (B
R, NBR, etc.) were charged into the Banbury and kneading was started. After 1 minute, carbon was charged, 3 minutes later, cleaning was performed, and after 5 minutes, the resin was taken out. A vulcanizing agent such as sulfur was charged with a roll (temperature: 55 ° C.) and extruded into a sheet. Vulcanization was performed at a mold temperature of 160 ° C. for 15 minutes to prepare a sheet-like sample, and vulcanization was performed at 160 ° C. for 20 minutes to prepare a cylindrical sample having a diameter of 1 inch and a height of 2 inches. A vulcanized sheet sample was punched out and subjected to a normal physical property and Gehman torsion test, and a dynamic servometer was used to measure a dynamic characteristic (tan δ) using a cylindrical sample. The results are shown in Tables 1 and 2.

[0020]

[Table 1]

[0021]

[Table 2]

As shown in Tables 1 and 2, natural rubber blended with a nitrile group-containing unsaturated copolymer rubber (NBR) (Example 1), or a styrene-butadiene copolymer rubber mixed therewith (SBR-2, bound styrene 40% by weight) (Example 3), and natural rubber blended with styrene-butadiene copolymer rubber (SBR-1, bound styrene 2.5% by weight) ( Comparative Example 1) shows good low-temperature characteristics, but the attenuation characteristics (tan δ) of Examples 1 and 3 are superior to Comparative Example 1.

Although the natural rubber blended with a relatively small amount of NBR (Example 2) and the natural rubber blended with SBR-1 (Comparative Example 1) have almost the same damping characteristics (tan δ). The low-temperature characteristics of Example 2 are superior to Comparative Example 1. The results obtained by blending NBR and SBR-1 in natural rubber (Example 3) and the material blended with SBR-2 in natural rubber (Comparative Example 2) show the attenuation characteristics (tan).
δ) are almost the same, but the low-temperature characteristics of Example 3 are superior to Comparative Example 2. The damping characteristics (tan δ) of the blend of natural rubber with NBR (Example 1) and the blend of natural rubber with a nitrile group-containing highly saturated copolymer rubber (HNBR) (Comparative Example 3) are almost the same. Although low, the low-temperature characteristics of Example 1 are superior to Comparative Example 3.

[0024]

The vibration-insulating rubber composition of the present invention is excellent in sound- and vibration-proof properties at room temperature to high temperature and low-temperature properties. Accordingly, the vibration-proof rubber composition is highly useful especially as a sound-proof and vibration-proof rubber product requiring cold resistance, for example, an engine mount for an automobile.

(Preferred Embodiment of the Invention) The rubber composition of the present invention, ie, (a) 50 to 95% by weight of an isoprene-based rubber and (b) an unsaturated copolymer rubber containing a nitrile group as a rubber component Preferred embodiments of the vibration-proof rubber composition comprising 50% by weight are summarized as follows.

(1) The isoprene-based rubber is natural rubber or polyisoprene. (2) isoprene-based rubber Mooney viscosity ML ₄ fifty to two
00, more preferably 70-100. (3) The nitrile group-containing unsaturated copolymer rubber is a copolymer rubber composed of an ethylenically unsaturated nitrile unit, a conjugated diene unit and / or a unit of an ethylenically unsaturated monomer, and the bond is unsaturated. The nitrile content is 10 to 40% by weight, more preferably 15 to 30% by weight.

(4) The nitrile group-containing unsaturated copolymer rubber has an iodine value of more than 120, more preferably 200 to 400. (5) The nitrile group-containing unsaturated copolymer rubber has a Mooney viscosity ML _{4 of} 150 or less, more preferably 80 or less. (6) The nitrile group-containing unsaturated copolymer rubber is a copolymer of an acrylonitrile unit and at least one selected from units of butadiene, isoprene and an ethylenically unsaturated monomer.

(7) The anti-vibration rubber composition comprises a total of 10 parts of an isoprene-based rubber and a nitrile group-containing unsaturated copolymer rubber.
Other rubbers of 50 parts by weight or less are contained with respect to 0 parts by weight. (8) In addition to the rubber component, the rubber component 1
Based on 00 parts by weight, 10 to 100 parts by weight of a reinforcing agent, 10 to 100 parts by weight of a filler, 5 to 50 parts by weight of a plasticizer, 0.01 to 5 parts by weight of an antioxidant, and 0.1 of a sulfur vulcanizing agent. 10 to 10 parts by weight, 0.1 to 10 parts by weight of a sulfur-based vulcanization accelerator and 0.1 to 20 parts by weight of a vulcanization aid.

[Brief description of the drawings]

FIG. 1 shows the cold-resistance characteristics (T10, vertical axis) and the damping characteristics (tan δ, horizontal axis) of the anti-vibration rubber compositions studied in Examples and Comparative Examples.

Claims (1)

[Claims] An anti-vibration rubber composition comprising (a) 50 to 95% by weight of an isoprene-based rubber and (b) 5 to 50% by weight of a nitrile group-containing unsaturated copolymer rubber as rubber components. Stuff.